COMPACT MID-IR LASER

• US 20090262768A1
• Filed: 01/15/2009
• Published: 10/22/2009
• Est. Priority Date: 06/15/2005
• Status: Active Grant

• Current Assignee: David F. Arnone, Timothy Day
• Original Assignee: David F. Arnone, Timothy Day
• Inventors: Day, Timothy, Arnone, David F.
• Granted Patent: US 7,873,094 B2
• Time in Patent Office: Days
• US Class Current: 372/36
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 3/00 Simple or compound lenses
• CPC Class Codes: G02B 7/023 permitting adjustment
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/02216 Butterfly-type, i.e. with electrode pins extending horizontally from the housings
• CPC Class Codes: H01S 5/02325 Mechanically integrated components on mount members or optical micro-benches
• CPC Class Codes: H01S 5/02415 by using a thermo-electric cooler [TEC], e.g. Peltier element
• CPC Class Codes: H01S 5/02492 CuW heat spreaders
• CPC Class Codes: H01S 5/0427 for applying modulation to the laser
• CPC Class Codes: H01S 5/06226 Modulation at ultra-high frequencies
• CPC Class Codes: H01S 5/3401 having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers

Abstract

A compact mid-IR laser device utilizes a quantum cascade laser to provide mid-IR frequencies suitable for use in molecular detection by signature absorption spectra. The compact nature of the device is obtained owing to an efficient heat transfer structure, the use of a small diameter aspheric lens and a monolithic assembly structure to hold the optical elements in a fixed position relative to one another. The compact housing size may be approximately 20 cm×20 cm×20 cm or less. Efficient heat transfer is achieved using a thermoelectric cooler TEC combined with a high thermal conductivity heat spreader onto which the quantum cascade laser is thermally coupled. The heat spreader not only serves to dissipate heat and conduct same to the TEC, but also serves as an optical platform to secure the optical elements within the housing in a fixed relationship relative on one another. A small diameter aspheric lens may have a diameter of 10 mm or less and is positioned to provided a collimated beam output from the quantum cascade laser. The housing is hermetically sealed to provide a rugged, light weight portable MIR laser source.

Claims

1. A mid-IR (MIR) laser device comprising:

a housing;

a thermo electric cooling (TEC) device contained within the housing;

a heat spreader coupled to the TEC within the housing;

a quantum cascade laser contained within the housing and fixedly coupled to the heat spreader, the quantum cascade laser generating light output; and

an optical lens contained within the housing and fixedly coupled to the heat spreader, the optical lens collimating the light output from the quantum cascade laser, wherein the optical lens has numerical aperture that is greater than approximately 0.6, a diameter of less than approximately 5 millimeters, and a focal length of less than approximately 5 millimeters;

wherein the heat spreader serves to distribute heat to the TEC and also serves as an optical platform to fixedly position the quantum cascade laser and the optical lens relative to one another.

2. The MIR laser device of claim 1 within the housing is positioned (1) above a top surface of the TEC or (2) above an intermediate plate positioned between the top surface of the TEC and the heat spreader.

3. The MIR laser device of claim 1 wherein the housing has dimensions of less than approximately 20 centimeters by 20 centimeters by 20 centimeters.

4. The MIR laser device of claim 1 wherein the housing has dimensions of less than approximately 3 centimeters by 4 centimeters by 6 centimeters.

5. The MIR laser device of claim 1 wherein the heat spreader has a thermal conductivity approximately 150-400 W/mK.

6. The MIR laser device of claim 1 further comprising a high thermal conductivity sub-mount positioned between the quantum cascade laser and the heat spreader, the sub-mount having a thermal conductivity of approximately 500-2000 W/mK.

7. The MIR laser device of claim 1 further comprising an electronics sub-assembly comprising:

a switch contained within the housing;

an summing node, contained within the housing;

an RF input port for inputting an RF modulating signal;

a drive current input terminal electrically connected to the quantum cascade laser for inputting drive current to the quantum cascade laser;

a switching control signal input terminal for inputting a switching control signal for switching the switch between a first and second state;

the switch electrically connected to the quantum cascade laser and operative in a first state to turn the quantum cascade laser on and in a second state operative to turn the quantum cascade laser off;

the summing node interposed in an electrical path between the drive current input terminal and the quantum cascade laser to add the RF modulating signal to the drive current.

8. A laser device comprising:

a heat spreader;

a laser coupled to the heat spreader, the laser generating light output; and

an optical lens coupled to the heat spreader, the optical lens collimating the light output from the laser, wherein the optical lens has numerical aperture that is greater than approximately 0.6, a diameter of less than approximately 5 millimeters, and a focal length of less than approximately 5 millimeters.

9. The laser device of claim 8 wherein the optical lens is made of a material selected from the group consisting of Ge, ZnSe, ZnS Si, CaF, BaF, and chalcogenide glass;

10. The laser device of claim 8 wherein the heat spreader serves to distribute heat and also serves as an optical platform to fixedly position the quantum cascade laser and the optical lens relative to one another.

11. The laser device of claim 8 further comprising a housing that retains the heat spreader, the laser, and the optical lens, the housing having dimensions of less than approximately 20 centimeters by 20 centimeters by 20 centimeters.

12. The laser device of claim 8 wherein the heat spreader has a thermal conductivity approximately 150-400 W/mK.

13. The MIR laser device of claim 8 further comprising a high thermal conductivity sub-mount positioned between the laser and the heat spreader, the sub-mount having a thermal conductivity of approximately 500-2000 W/mK.

14. A method for generating light output, the method comprising the steps of:

providing a heat spreader coupled to the TEC;

coupling a laser to the heat spreader, the laser generating light output; and

collimating the light output from the laser with an optical lens, the optical lens having numerical aperture that is greater than approximately 0.6, a diameter of less than approximately 5 millimeters, and a focal length of less than approximately 5 millimeters.

15. The method of claim 14 wherein the step of collimating the light output includes the optical lens being made of a material selected from the group consisting of Ge, ZnSe, ZnS Si, CaF, BaF, and chalcogenide glass;

16. The method of claim 14 further comprising the step of retaining the heat spreader, the laser, and the optical lens with a housing having dimensions of less than approximately 20 centimeters by 20 centimeters by 20 centimeters.

17. The method of claim 14 further comprising the step of positioning a high thermal conductivity sub-mount between the laser and the heat spreader, the sub-mount having a thermal conductivity of approximately 500-2000 W/mK.

18. A mid-IR (MIR) laser device comprising:

a housing;

a thermo electric cooling (TEC) device contained within the housing;

a heat spreader coupled to the TEC within the housing;

a quantum cascade laser contained within the housing and fixedly coupled to the heat spreader, the quantum cascade laser generating light output; and

an optical lens contained within the housing and fixedly coupled to the heat spreader, the optical lens collimating the light output from the quantum cascade laser;

wherein the heat spreader serves to distribute heat to the TEC and also serves as an optical platform to fixedly position the quantum cascade laser and the optical lens relative to one another.